Oceanic Airspace Procedures

by Mark Richards, , ,

Entering & Leaving Oceanic Airspace
Entry into Oceanic Controlled Aispace (OCA) is usually occurs at around 150-200nm from the coast, depending on the centre/approach controller's requirements. Inbound aircraft are usually handed off no later than 150nm from the coast, however this is again at the controller's discretion.

Speed Restrictions
Unless otherwise indicated or instructed, maximum speed below 10,000ft is 250 KIAS.

Transponder Operation
All Oceanic FIRs: Transponder should sqwawk last assigned code, or code 2000 if none assigned.

Cruising Levels
http://www.vatpac.org/vat-dean/oceanic/levelsoc.gif∞

Subject to traffic, the controller may issue an aircraft with a Block Clearance between two flight levels. When this is issued, the aircraft may operate at any altitude between the two levels, even if it is not a standard flight level (eg FL347 for a block clearance between FL310 and FL370). During the position reports, the pilot must announce that he is "In the block between FLxxx and Flxxx," but the exact level at which he/she is flying need not be reported

RVSM
As of early November 2001, all Brisbane, Auckland, Tahiti and Nadi oceanic airspace has been designated RVSM (Reduced Vertical Separation Minima) airspace, with new aircraft cruising levels as shown in the images below. Aircraft capable of RVSM are to note this capability in their flightplan. Vertical separation between two RVSM-equipped aircraft is 1000ft, however should only one or none of the aircraft have RVSM capability, 2000ft should still be used. Lateral separation remains unaffected. See image below for table of RVSM cruising levels. Pilots should be aware of the need to re-plan their cruise levels should they transition between RVSM and non-RVSM airspace.

Separation
The controller must ensure that there is a minimum longitudinal (horizontal) separation of 15 minutes or more between aircraft on the same or crossing tracks, as well as a minimum of 2000ft vertical separation. Horizontal separation can be obtained by ensuring that, in the case of two aircraft flying the same track in the same direction and level, the first aircraft's estimate for the NEXT common position is at least 15 minutes earlier than the following aircraft's estimate for that same position. If a discrepancy is found it is up to the controller to either ask for a level change or to impose a mach number restriction on the following aircraft.

Indian Ocean Random RNAV Area (IORRA)
Much of the airspace over the Indian Ocean between FL290 and FL410 is designated as the Indian Ocean Random RNAV Area. Aircraft operating in this area should plan on User Planned Routes (UPRs) between the gates on each side. This affects flights between Australia & South Africa and Australia & Mauritius.

The northern boundary of the zone runs from:

S30 04.0 E112.45.1 (MERIB)
S20 00.0 E102 10.0
S20 00.0 E100 00.0
S10 00.0 E100 00.0
S10.00.0 E090 00.0
S20 00.0 E060.00.0
The southern boundary is S90 00.0

Flights must plan via the Perth Entry/Exit gates at waypoints MERIB, STUGE or SHEMP.

Flight plans must indicate waypoints at the crossing of each 5? of longitude

Position reports are required at the entry/exit gate, 135?E, 125?E, 115?E, 105?E, 095?E, 085?E and 075?E

Gates on the western side of the Indian Ocean Random RNAV Area are SOLIT, MABAD, GUGON, SUNKI and RERAB

Tasman Sea User Preferred Routes
The Tasman Sea will move from published airways to User Preferred Routes (UPRs) in the near future, implementation is planned in real-life at this time for November 2003. This system will allow aircraft and operators to fly any chosen route between gates that will be established on either side of the Tasman without reference to airways or waypoints. It is envisaged that reporting requirements will be similar to those in the Indian Ocean Random RNAV Area. As details of this system are announced, their implementation into VATPAC operations will be detailed. Watch this space!

Aircraft Callsigns
Most aircraft you will see in the VATPAC region will be Australian or New Zealand Registered:
Australia: VH- prefix, e.g. VH-ABC
New Zealand: ZK- prefix e.g. ZK-DEF

Alternatively, Flight Number Callsigns (FNCs) will be used. They consist of the airline's two letter designator, followed by the flight number. Here are some examples which you are likely to find in the SATPAC region.

QANTAS: QF or QFA - prefix, e.g. QF100 = Qantas Flight 100 (Voice - Qantas 100).
Air New Zealand: NZ or ANZ - prefix e.g. NZ200 = Air New Zealand Flight 200 (Voice - New Zealand 200).
Ansett Australia: AN or AAA - prefix e.g. AN300 = Ansett Australia Flight 300 (Voice - Ansett 300).

Oceanic Air Traffic Control Procedures
Oceanic Air Traffic Control is essentially quite simple. At each waypoint along the aircraft's track, the pilot makes a position report to the oceanic centre giving his time over the waypoint, the estimated time over the next waypoint, and the name of the waypoint after that. He will also give his mach number, groundspeed, wind and temperature details, though the weather details are optional in some cases (they are not required for SATPAC ops). The following is a sample position report.

Pilot: Brisbane Radio, QANTAS 51 position on 128.6
(Qantas 51 is calling Brisbane on frequency 128.6 to give his report).

ATC: QANTAS 51, Brisbane, go ahead.

Pilot: QANTAS 51 is position ANULI at time 1002, Flight Level 350, estimating VIROG at 1042, IGEVO next. Mach decimal 84, groundspeed 510. Wind 160 diagonal 15, temperature minus 25. Go ahead.
(Qantas 51 is at position ANULI at time 1002 (UTC) at FL350. He will pass position VIROG at 1042 (UTC) and the next position after that is IGEVO. He is flying at Mach .84, and his groundspeed is 510 knots. The wind at his position is 160 degrees at 15 knots and the temperature is -25 degrees Celsius ).

ATC: QANTAS 51 roger Brisbane.

SELCAL
Due to the background noise level experienced on HF radio frequencies, air crews usually prefer to turn down the audio level of their HF receiver. To initiate contact ATC uses Selective Calling or SELCAL. SELCAL uses a unique (for each aircraft) 4-letter code (eg. QR-AC) transmitted over the communications frequency to sound an alert for the flightcrew.

When ATC wishes to communicate with an aircraft, they will send a single SELCAL message to the flight. All aircraft monitoring that channel receive the SELCAL broadcast, which consists of two tones, but only the intended recipient will hear the "Ding Dong" of an incoming message. When alerted by SELCAL, the crew then turn up thier HF radio to communicate with ATC. The crew must then ensure that the message is intended for them, responding using ICAO recommended radio procedures. In VATPAC operations the controller will initiate contact with an aircraft by using a text message to simulate a SELCAL. The intended recipient will hear the "Ding Dong" of an incoming text message. The message will usually consist of just the word "SELCAL", but occasionaly may also include an instruction to make contact with the relevant controller. On receipt of the SELCAL message pilots should then contact the controller using voice. There is no need to reply with a private text message.

e.g. initial SELCAL check by Oceanic:

[BN-T_O_FSS] ?Whiskey Tango Tango good afternoon, Brisbane accepts Primary guard this frequency, secondary 122.1, standby SELCAL check."
Wait for the SELCAL check before you reply...
{BN-T_O_FSS -> WTT: SELCAL}
[PILOT] ?SELCAL check OK, secondary 122.1, Whiskey Tango Tango"
[BN-T_O_FSS] ?Whiskey Tango Tango. Request your estimate for position VIROG"
From now on ATC will preface all communications with a text SELCAL, to which the pilot responds by voice:
{BN-T_O_FSS -> WTT: SELCAL}
[PILOT] "Auckland Radio, Victor Tango Tango on 128.6 answering SELCAL"
[NZZO_O_FSS] "Victor Tango Tango, from control: Climb to and maintain FL380 non-standard, report reaching."
[PILOT] "Auckland, Victor Tango Tango leaving FL370 for FL380, will report reaching."